TV Land said Tuesday Shaughnessy will guest star as Gregory, a possible love interest for both Drescher's character and her gay ex-husband Peter, played by John Michael Higgins.
The episode is to air Aug. 17.
"Happily Divorced" is based on Drescher's own life. It is about a woman whose 18-year marriage ends suddenly when her husband announces he's gay, but can't afford to move out of the marital home.
"The Nanny" ran from 1993 to 1999. In the sitcom, Drescher played a New York nanny who ultimately marries the wealthy father of the three children she watches. Shaughnessy played the dad.
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